Materials for refractories

Even small amounts of microsilica will improve the flow properties of a castable. The dense particle packing achieved by microsilica additions will minimise the amount of water needed for casting. This gives low porosity and high strength properties in the fired product.

• The use of particle size distribution in development of refractory castables.
• Particle size distribution and its relevance in refractory castables.
• Particle size and particle size distribution of microsilica and its relevance to technical applications.
• The effect of particle-size distribution on flow of refractory castables.

Technical papers: Particle Packing.

Due to their small particle size, microsilica particles fill the voids between larger aggregates and give dense castables. A denser castable has lower permeability, higher strength and higher thermal conductivity.

The reactivity of microsilica particles combined with their fine distribution allows for a more efficient cement reaction, i.e. optimising the effects of a low cement content.

For more information you can read our research papers:

• The use of particle size distribution in development of refractory castables.
• Particle size distribution and its relevance in refractory castables.
• Particle size and particle size distribution of microsilica and its relevance to technical applications.

Technical papers: Particle Packing.

When mixing microsilica with water, some of the surface molecules dissociate and enable a coagulation of microsilica particles. A network of coagulated particles form a thickening gel which gives improved green strength for castables with very low cement contents. Additionally, the gel structure assures strength during heat-up by counteracting the strength degradation caused by dehydration of cement at temperatures between 200-800°C.

For more information you can read our research papers here:

• The Use of Microsilica in Refractory Castables.
• Microsilica - A Versatile Refractory Raw Material.
• The effect of microsilica additions on flow and strength of tabular alumina based refractory castables.

Mullite bond-phase is beneficial for high temperature properties in alumina-silicate systems.

In castables the mineralogical make-up of the bond-phase goes through several intermediates during heat-up before

ending up with the desired physical and mineralogical properties at service temperature.

If the composition of the bond phase is incorrect, the result may lead to softening and refractory failure at a much lower temperature than anticipated.

A key to proper design is adequate microsilica content.

You can find more information here:
Research papers:  Let us Make a Mullite Matrix.
Technical papers: Mullite Formation.

The submicron, amorphous microsilica particles are highly reactive during sintering which results in improved ceramic bonding at reduced firing temperatures.

In alumina based castables, microsilica reacts with alumina to form mullite. This crystalline phase has high refractoriness, and gives a castable high mechanical strength at service temperatures up to 1800°C.

For more information you can read our research papers here:

• Correlation between mullite formation and mechanical properties of refractory castables at elevated temperatures.
• Castables with MgO-SiO2-Al2O3 as bond phase.
• Mullite formation in tabular alumina based refractory castables with hydraulic alumina as binder.

Technical papers: Mullite Formation.